Plasma Surface Modification of Polyhedral Oligomeric Silsequioxane-Poly(carbonate-urea) Urethane with Allylamine Enhances the Response and Osteogenic Differentiation of Adipose-Derived Stem Cells

This study present amino functionalization of biocompatible polymer polyhedral oligomeric silsequioxane-poly­(carbonate-urea) urethane (POSS-PCU) using plasma polymerization process to induce osteogenic differentiation of adipose derived stem cells (ADSCs). Optimization of plasma polymerization process was carried out keeping cell culture application in mind. Thus, samples were rigorously tested for retention of amino groups under both dry and wet conditions. Physio-chemical characterization was carried out using ninhydrin test, X-ray photon spectroscopy, scanning electron microscopy, and static water contact analysis. Results from physio chemical characterization shows that functionalization of the amino group is not stable under wet conditions and optimization of plasma process is required for stable bonding of amino groups to the POSS-PCU polymer. Optimized samples were later tested in vitro in short and long-term culture to study differentiation of ADSCs on amino modified samples. Short-term cell culture shows that initial cell attachment was significantly (<i>p</i> < 0.001) improved on amine modified samples (NH₂-POSS-PCU) compared to unmodified POSS-PCU. NH₂-POSS-PCU samples also facilitates osteogenic differentiation of ADSCs as confirmed by immunological staining of cells for extracellular markers such as collagen Type I and osteopontin. Quantification of total collagen and ALP activity also shows significant (<i>p</i> < 0.001) increase on NH₂-POSS-PCU samples compared to unmodified POSS-PCU. A pilot study also confirms that these optimized amino modified POSS-PCU samples can further be functionalized using bone inducing peptide such as KRSR using conventional wet chemistry. This further provides an opportunity for biofunctionalization of the polymer for various tissue specific applications

Development and characterization of thermally stable supported V–W–TiO₂ catalysts for mobile NH₃–SCR applications

<p>Vanadium based catalysts supported on a mixture of tungsten and titanium oxide (V₂O₅/WO₃–TiO₂) are known to be highly active for ammonia selective catalytic reduction (NH₃–SCR) of NO_x species for heavy-duty mobile applications. However they are also known to be sensitive to high temperatures which leads to both sintering of the anatase TiO₂ support and a first order phase transition to rutile at temperatures >600°C. Here we report our attempts to use SiO₂ to stabilize the TiO₂ anatase phase and to compare its catalytic activity with that of a non-stabilized V₂O₅/WO₃–TiO₂ catalyst after thermal aging up to 800°C. Detailed characterization using spectroscopic (Raman, UV–vis, X-ray absorption spectroscopy), scattering and techniques providing information on the catalytic surface (Brunauer–Emmet–Teller, NH₃ adsorption) have also been performed in order to understand the impact of high temperatures on component speciation and the catalytic interface. Results show that non-stabilized V₂O₅/WO₃–TiO₂ catalysts are initially stable after thermal aging at 600°C but on heating above this temperature a marked drop in catalytic activity is observed as a result of sintering and phase transformation of Anatase into Rutile TiO₂ and phase segregation of initially highly dispersed WO₃ and polymeric V₂O₅ into monoclinic WO₃ and V₂O₃ crystallites. Similar behavior was observed for the 4–5 wt-% of SiO₂-stabilised sample after aging above 700°C, importantly therefore, offset by some ∼100°C in comparison to the unstabilised sample.</p

Visible Light Photo-oxidation of Model Pollutants Using CaCu₃Ti₄O₁₂: An Experimental and Theoretical Study of Optical Properties, Electronic Structure, and Selectivity

Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu₃Ti₄O₁₂ has distinct octahedral Ti⁴⁺ and square planar Cu²⁺ sites and is thus a candidate material for this approach. The sol−gel synthesis of high surface area CaCu₃Ti₄O₁₂ and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO₄ units within the structure of CaCu₃Ti₄O₁₂) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu₃Ti₄O₁₂ which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃